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Dave Liebl was doubtful about building a dam in the middle of a field, but his wife Karen convinced him that something had to be done to halt the gully erosion eating away their topsoil. “Now I think it’s one of the best things I’ve done.”

The Liebls’ first two water- and sediment-control dams were so effective at halting gully erosion that they invested in five more for other fields. “We haven’t lost one bit of production from the dams,” says Dave. On the contrary, he says, before the sediment dams were installed, “there were places where we didn’t get a crop because of the gully.”

To other doubters, Dave says: “Some complain about having to farm around them, but it’s a small price to pay for keeping your soil.”

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Water- and sediment-control basins are a time-tested way to prevent field gullies in hilly fields with irregular topography, says Jeff Hellermann, NRCS district conservationist, Stevens County, Minn.

Photo: Liz Morrison

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Year after year, Donnelly, Minn., farmer Dave Liebl would close the gully that formed in one of his fields, only to have it reopen. “I’d dig it, and it would look smooth. Then after a hard rain, there’d be another gully in the same place.” The ditch below the field had silt several feet deep.

The Liebls installed two water- and sediment-control basins in the field to slow the speed of water flowing through the draw. These short, earthen dams bridge the drainage-way, preventing runoff water from cutting a new channel. The dams, which are 3-4 ft. high, are broad enough to be farmed on both banks. Now, the Liebls’ soil stays put, and the field — minus the gully — is more farmable. “It works so well, I can’t say enough good about it,” Dave says.

Water- and sediment-control basins, or WASCOBs, are a time-tested way to halt gully erosion with little or no loss of productive cropland, says Jeff Hellermann, NRCS district conservationist in Stevens County, Minn. They also improve drainage water quality and boost crop production in fields with irregular topography, he says.

Hellermann is seeing renewed interest in the practice these days, in part because the region has experienced more pounding rainfalls in the last few years. These intense rainstorms carve out small gullies, which then transport field runoff laden with sediment, fertilizer and other pollutants.

“A lot of growers disk them closed,” says Scott Wallace, NRCS district conservationist in Peoria County, lll. “But they tend to show up again and again, even with no-till.” Illinois Soil Conservation transect surveys estimate that gully erosion occurs on about 20-25% of fields in the state.

“Ephemeral gullies , are a substantial source of sediment leaving fields,” says Matt Helmers, Iowa State University (ISU) agricultural and biosystems engineer. “And we’re seeing more of them in recent years.”

The Upper Midwest’s climate is getting wetter, and the number of severe downpours is on the rise, notes Agronomist Richard Cruse, director of ISU’s Iowa Water Center. “Today’s soil erosion rates are expected to increase disproportionately as precipitation continues to rise,” he says. “A 20% increase in precipitation has been shown to increase erosion rates by an estimated 37%.”

Helmers adds: “We are taking out a lot of grassed waterways that might have provided some protection from gully erosion.”